CADILLAC ESCALADE ESV FUEL INJECTOR PROBLEM

2003 Cadillac Escalade Esv • 125,000 miles

Have a misfire detected during driving at moderate speed, but not during idle or slower driving. I've heard that not having the gas cap tight or air filter housing secured can cause this, but I've looked at those and they seem okay. Checked the plug wires to make sure they're on & seem to be. I've also heard that a stuck fuel injector can cause this and is there a fuel injector cleaner available that may help fix this problem? The diagnostic code is P0300B (I have a code reader)

I also have a code (U1041C) loss of ECBM communication. What exactly is that?